1. Field of the Invention
This invention relates to an improved process for the production of defoamer compositions, and more particularly, to the production of defoamer compositions using a high energy, in-line mixer apparatus therefor.
2. Discussion of Related Art
When carrying out industrial processes for which aqueous or substantially aqueous media are used, there frequently occur troublesome foams which, for example, can retard the speed of the process and impair the quality of the process products. Typical processes which are affected by these troublesome foams are, for example, processes for manufacturing and finishing paper, processes for finishing and dyeing various substrates, in particular textile materials, processes for manufacturing and applying paints, and also those processes for purifying and processing effluents by mechanical, chemical or biological means, which are carried out in conventional waste water purification plants.
To this end it is known to use antifoams, for example silicone oils, palm oil, linseed oil, lower alkyl glycols, and block copolymers of lower alkylene glycols in order to prevent foam formation or to break down foam that has formed. Such antifoams or defoamer compositions may comprise a single component or multiple components which may be combined by simply mixing together. However, many defoamer components are water-insoluble and thus some defoamer compositions contain the defoamer components in dispersion requiring intense mixing to produce the final defoamer composition.
Thus, dispersions of solid particles in water-insoluble organic liquids have been widely used for controlling foam in aqueous systems. Such dispersions usually employ agents to facilitate the spreading of the dispersions at the interface of the aqueous system with air. Anionic, cationic and nonionic surfactants have been used for this purpose. These surfactants include such diverse materials as fatty acid soaps, amine salts, polyethylene oxide condensation products, polyethylene glycol esters and silicone oils. These spreading agents, although they increase the cost of a defoamer, often produce undesirable side effects, e.g., a loss of defoaming ability or an increase in viscosity when the defoamer is heated or stored for long periods of time.
One such composition for controlling foam in aqueous systems is disclosed in U.S. Pat. No. 3,951,853. The composition therein contains from about 75 to about 98 parts by weight of an organic liquid, from about 1 to about 15 parts by weight of small, solid particles of an amide suspended in the organic liquid, from about 0.1 to about 10 parts by weight of a base, from about 0.1 to about 5.0 parts by weight of a reactive chlorosilane monomer and from about 0 to about 3 parts by weight of an organic component. The amide is a reaction product of a polyamine having at least one alkylene group of 2 to 10 carbon atoms and the organic component is an organic polymer or a fatty acid of 10 to 20 carbon atoms or a glyceride of fatty acids of from 10 to 20 carbon atoms.
This composition is obtained by first preparing a pre-emulsion in an organic liquid by vigorously mixing a solution or a dispersion of the base in an organic liquid with a solution of the reactive chlorosilane. The finely divided amide particles are then dispersed in the pre-emulsion. The amide may be jet-milled to yield the finely divided particles which can simply be mixed into the above pre-emulsion. An alternate process described in U.S. Pat. No. 3,677,963, Lichtman et al, patented Jul. 18, 1972, may be used to produce the small particles of amide in the pre-emulsion. That process when applied to the compositions of the invention involves heating the amide with a viscosity reducing amount of chlorosilane monomer in sufficient organic liquid and from 0 to 3 parts by weight organic component to obtain a uniform homogenous melt and pouring the resulting melt into a cooling liquid, in this case, the pre-emulsion. The resulting suspension of amide particles may then be homogenized to form a stable dispersion wherein the reaction products of the base and chlorosilane function as dispersing and spreading agents. Such products based solely on an amide hydrophobe may be prepared by simply quenching a concentrated solution of melted amide in an organic component into a larger volume of organic components under controlled temperature conditions. In addition, other hydrophobic defoaming components such as hydrophobic silica may be employed. However, such dispersed defoamer compositions require a long cycle time for preparation, typically in a batch unit high-shear mixing apparatus which limits production capacity. In addition, optimum dispersion of the defoaming components is required to produce the desired particle size distribution necessary for defoamer compositions. In addition, it is sometimes necessary to further process the defoamer compositions in an expensive and high-maintenance homogenizer as well.
One type of mixing unit is a static mixer, also known as an interfacial surface generator. An interfacial surface generator is a static device which mixes fluids by passage of the fluid through the interfacial surface generator. Such mixing is obtained by division of the stream into a plurality of substreams or branches, recombination of the substreams into a main stream and subsequent division, repositioning and recombination until the desired degree of mixing has been obtained. Several interfacial surface generators are known and set forth for example, in U.S. Pat. No. 3,404,869. Such devices employ baffles positioned within a conduit to provide the desired division, repositioning and recombination. However, these devices do not supply the energy necessary to break up particles, especially when particle sizes less than 100 microns are desired.
It would be desirable if there were available a mixing device and a process which could provide the degree of mixing of streams controlled by ready variation of its parameters, and provide the energy input required to break up particles to micron size.
In addition, it would be highly desirable to avoid the afore-noted drawbacks of the present state of the art and provide a process for producing defoamer compositions which overcomes these disadvantages.